1. Field of the Invention
The present invention relates to a sheet conveyance apparatus, a sheet processing apparatus, and an image forming apparatus, and in particular, to a sheet conveyance apparatus, a sheet processing apparatus, and an image forming apparatus which can recover a jammed sheet easily without damaging the sheet.
2. Description of the Related Art
Heretofore, in image forming apparatuses such as a copier, in order to save the time and effort of, for example, binding to sheets after image formation, there are those including a sheet processing apparatus which takes sheets after image formation sequentially into the apparatus, and performs binding or the like to these sheets.
Then, such sheet processing apparatuses, some have a function of conveying sheets into an intermediate stack portion by a sheet conveyance apparatus, aligning ends of the sheets in the intermediate stack portion, and binding the sheets by a binding unit, such as a stapler (for example, refer to U.S. Pat. No. 6,997,456).
FIG. 16 illustrates construction of a sheet processing apparatus including such a conventional sheet conveyance apparatus. A sheet S on which an image is formed is conveyed into an intermediate stack portion 101 by an intermediate roller 102. Then, the sheet which is stacked in the intermediate stack portion 101 in this way is returned to a direction reverse to a conveyance direction by a return unit not illustrated to abut on an alignment reference wall 104, and alignment of rear ends in the conveyance direction is performed.
By the way, when a sheet is conveyed, when a preceding sheet S previously stacked in the intermediate stack portion 101 floats above a nip line of the intermediate roller 102, a subsequent sheet collides with the preceding sheet S, and alignment may be disordered or a jam may be generated.
Then, conventionally, a rear end presser member 103 is provided so as to prevent a lift of a rear end portion of the preceding sheet S, and this rear end presser member 103 presses the rear end portion of the preceding sheet S stacked in the intermediate stack portion 101. In addition, in order to restrict a position of the rear end of the preceding sheet S by a bottom end and to prevent the lift, this presser member 103 is rotatably provided downstream from a nip position of the intermediate roller 102 while being urged in a direction reverse to a sheet conveyance direction shown by an arrow B.
Then, until the presser member 103 is pressed by an end of the subsequent sheet to rotate, a rear end of the preceding sheet S is located below the nip line of the intermediate roller 102 by such the presser member 103. Thereby, when the presser member 103 rotates, the end of the subsequent sheet has been already conveyed to the downstream from the rear end of the preceding sheet S, and hence, the end of the subsequent sheet never collides with the rear end of the preceding sheet S.
By the way, when a jam is generated in the intermediate stack portion 101 of the sheet processing apparatus with such construction, a user puts his/her hand into the intermediate stack portion from a sheet discharge port 105, provided downstream in the sheet conveyance direction, to take out a jammed sheet.
By the way, in such conventional sheet conveyance apparatuses, sheet processing apparatuses, and image forming apparatuses, some may have an intermediate stack portion which is too long in a conveyance direction for a user's hand to reach its back. In addition, for example, in the case of an intra-body sheet discharge type apparatus in which an image scanner is arranged with a space being provided in an upper portion of a main body of an image forming apparatus, since the image scanner restricts a vertical direction, it is hard to access the intermediate stack portion from a sheet discharge port.
Hence, in order to increase operability including also a case of processing sheets which are accumulated in the intermediate stack portion, it is necessary to enable to perform jam recovery in the intermediate stack portion from the downstream in the sheet conveyance direction as well as from the upstream of an intermediate conveying roller.
Then, conventionally, for example, a jam recovery cover not illustrated is provided upstream from the intermediate stack portion. Then, when a rear end of the jammed sheet projects upstream from the intermediate roller 102, jam recovery is performed by opening the jam recovery cover and drawing out the sheet from the upstream of the intermediate conveying roller.
Here, when jam recovery is performed from the upstream of the intermediate conveying roller in this way, the jammed sheet is processed by being drawn in a direction reverse to the sheet conveyance direction. But, in the vicinity of the intermediate conveying roller, a lot of small parts are arranged in a narrow space, for example, in order to suppress curl of a sheet.
For this reason, when trying to recover the jammed sheet with drawing the jammed sheet in the reverse direction, for example, a strong force is applied in the direction reverse to the sheet conveyance direction to the presser member 103 which is constructed so as to be easy to rotate in the sheet conveyance direction. Hence, there is a possibility that the presser member 103 may be damaged.
For this reason, in the case of performing jam recovery, it is necessary to remove the jammed sheet with paying attention to the presser member 103 and taking time. Hence, the jam recovery takes time and effort. In addition, it leads to a cost hike that reinforcement of the presser member 103 is performed so that the presser member 103 may not be damaged.
In addition, there were problems that the presser member 103 was damaged by a user touching the presser member 103 at the time of jam recovery, and that the presser member 103 caught a jammed sheet to tear the jammed sheet, a part of which was left in the intermediate stack portion. Furthermore, in conventional construction, unless a rear end of a sheet projected from the intermediate conveying roller to the upstream, jam recovery from the upstream in the sheet conveyance direction was not completed.